The present invention relates to an arrangement for setting the starting torque of an elevator machinery.
In an elevator arrangement consisting of an elevator car, a counterweight and an elevator machinery driving there, there are large variations in the imbalance moment. Generally, every time when the car stops at a landing, its load changes, causing a change in the imbalance moment of the elevator arrangement, as the starting torque of the motor of the elevator machinery must always be set in accordance with the prevailing load.
At present, the required starting torque is determined using e.g. a load weighing device in the car. In this case, a power sensor is placed between the car and the car frame to weigh the load. This structure is difficult to apply in the new elevators having a so-called frameless car structure with an integrated car and car frame. In addition, long transmission lines are needed between the car and the control system and they are exposed to various disturbances. Likewise, this design does not take the weight of the ropes and the friction on the guide rails into account.
Another alternative is to use a brake balance system. In this case, the brake torque of the elevator is measured and the starting torque is set to the same magnitude. After this, the brake is released when the motor generates a torque that brings the brake torque to zero. Although this solution works well, it is expensive because of the friction at the hinges and the non-ideality of the brake shoe.
A third alternative is to use a weighing device suspended at the end of a rope. In this case, the force acting on the point of suspension is measured. A drawback is that, in the case of 1:1 suspension, the rope end moves. This drawback is not present in 1:2 suspension, but the friction of the guides gives rise to errors.
The object of the present invention is to eliminate the drawbacks described above. A specific object of the present invention is to disclose a new type of elevator arrangement for setting the starting torque of the motor of the an elevator machinery, an arrangement which accurately measures actual forces and which can be implemented in a simple way with few components and short transmission lines.
In the elevator arrangement of the invention for setting the starting torque of the motor of an elevator machinery, the elevator machinery is fixed to a guide rail in an elevator shaft. According to the invention, the elevator arrangement comprises at least one power sensor connected to the elevator machinery via a non-switched connection and designed to determine the imbalance moment that the prevailing car load produces in the elevator machinery.
Thus, in the elevator arrangement of the invention, no car load measurements need to be made in the car itself to determine the required starting torque of the motor, but instead the measurements can be performed using appropriate power sensors, which are placed on immobile points in the framework structures of the elevator machinery and in parts of the elevator arrangement fixedly connected to them.
Thus, one or more power sensors may be installed e.g. in places like the following: elevator machinery, guide rail fixture of the elevator machinery, beating carrier of the elevator machinery and the guide rail in the elevator shaft to which the elevator machinery is fixed.
The elevator arrangement of the invention has significant advantages as compared with prior art. It makes it possible to measure the actual forces acting on the machinery, which are not transmitted via ropes or the like and are not liable to errors e.g. due to friction. Moreover, the sensors can be mounted near the machinery and therefore also near the control equipment, so the transmission lines will be short.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.